CN111823719A

CN111823719A - Systems and techniques to reduce debris buildup around printhead nozzles

Info

Publication number: CN111823719A
Application number: CN202010307009.2A
Authority: CN
Inventors: 弗朗西丝·H·本顿; 阿尔俊·温卡塔拉马南
Original assignee: Markem Imaje Corp
Current assignee: Markem Imaje Corp
Priority date: 2019-04-19
Filing date: 2020-04-17
Publication date: 2020-10-27
Anticipated expiration: 2040-04-17
Also published as: CN111823719B; US11186086B2; US20200331263A1; EP3725535A1

Abstract

Systems and methods for industrial printing, such as using a Drop On Demand (DOD) inkjet printhead, in at least one aspect, a printing apparatus comprising: a printhead configured to selectively eject liquid through a plurality of nozzles to form an image on a moving substrate; and a printhead enclosure configured to contain a pressurized air space at least in front of the plurality of nozzles of the printhead; the printhead enclosure includes a slot aligned with the plurality of nozzles to allow the selectively ejected liquid to pass through the slot when the selectively ejected liquid is ejected toward the moving substrate; and the printhead enclosure is configured to contain the pressurized air space and to cause an airflow through the slot at a flow rate to prevent dust and debris from entering the slot as the selectively ejected liquid passes through the slot and as the airflow, without the direction of the selectively ejected liquid being impeded by the airflow.

Description

Systems and techniques to reduce debris buildup around printhead nozzles

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No. 62/836,235, filed 2019, 19.4, the entire contents of which are hereby incorporated by reference. This application also claims priority from us provisional patent application No. 62/925,746, filed 24.10.2019, the entire contents of which are incorporated herein by reference. This application further claims priority from U.S. utility patent application serial No. 16/850,964, filed on even 16/4/2020, the entire contents of which are hereby incorporated by reference.

Technical Field

This specification relates to industrial printing systems, and more particularly to systems and techniques related to drop-on-demand (DOD) inkjet printheads.

Background

Various industrial printing techniques are known and enable printing of important information on the packaging (e.g., for sale by date). DOD inkjet printheads have been used to print images on commercial products using various types of inks, including hot melt inks. These images may include graphics, company logos (logos), alphanumeric codes and identification codes. Such images are readily observable, for example, on corrugated containers filled with consumer goods. In addition, during the printing of such images, dust particles in the factory air typically land on the nozzle plate of the DOD printhead and then clog the nozzle. This can lead to unprinted lines across the print due to nozzle blockage, which in turn can lead to reduced print quality. To avoid this, users of conventional DOD printheads often clear the printhead. Purging involves forcing out an amount of ink from the nozzle to dislodge debris. To achieve high quality printing requirements, the printer may be set to automatically clear after multiple prints, for example every 1000 prints, and in some cases, clearing may be required after only 50 prints. In some cases, small purges may be performed between each print. Purging interrupts the printing operation and consumes ink.

In addition, the removed ink must be handled in some way. One approach is to place a movable drip tray under the nozzles to capture the purged ink, where the movable drip tray is held in place by a bracket attached to the exterior of the printhead. In some cases, a drip guard may be used to help direct the purged ink away from the production and/or packaging line and into a removable drip tray. Another approach is to capture and recycle the ink, for example using air blows to push the purged ink into channels on the sides of the printhead during purging, and vacuum to pull the purged ink to a filter and back into a clean ink supply.

Disclosure of Invention

This specification describes technologies relating to industrial printing systems, and in particular systems and technologies relating to Drop On Demand (DOD) inkjet printheads used in manufacturing or dispensing facilities. The inkjet printhead enclosure may be pressurized to direct a flow of air through a slot in front of the nozzle plate to improve operation of the printhead. As described herein, a printhead enclosure for a hot melt DOD printhead may employ various slot designs, where the slots are aligned in front of the nozzles for ink ejection for printing, and the printhead may have an on-board pressure source with an air intake filter.

Typically, one or more printing devices include: a printhead configured to selectively eject liquid through a plurality of nozzles to form an image on a moving substrate; and a printhead enclosure configured to contain a pressurized air space at least in front of the plurality of nozzles of the printhead; the printhead enclosure includes a slot aligned with the plurality of nozzles to allow the selectively ejected liquid to pass through the slot when the selectively ejected liquid is ejected toward the moving substrate; and the printhead enclosure is configured to contain the pressurized air space and to cause an airflow at a flow rate through the slot to prevent dust and debris from entering the slot when the selectively ejected liquid passes through the slot and when the airflow (e.g., the airflow always flows through the slot when the printer is powered up) without the direction of the selectively ejected liquid being impeded by the airflow. These and other embodiments can optionally include one or more of the following features.

The printing device may comprise a smooth and straight inner surface on each of at least two sides of the slot. The pressurized air space is set at a pressure level such that the flow rate of air through the slot interrupts a Couette flow (Couette flow) caused by the moving substrate passing the print head and reduces satellite droplets (satellite drops) entrained in the Couette flow. The printhead enclosure includes a curved outer surface on at least a leading edge of the slot. The slot and the curved outer surface are each integral (integrally molded) with the printhead enclosure. The printhead enclosure may include a separator, and the slot and the curved outer surface are each integral (integrally molded) with the separator. And the separator is configured to slide in and out of the printhead enclosure.

The printhead enclosure may include: the curved outer surface on each of the leading and trailing edges of the slot, the curved outer surface having a radius of curvature determined to produce a uniform flow distribution between the opening of the slot and the moving substrate; and a distance between two inner sides of the slot, the distance being determined to prevent the liquid from contacting the two inner sides of the slot and to maintain a consistent, non-turbulent air flow through the slot. The radius of curvature is between 1.0 millimeter and 2.0 millimeters, each of the two inner sides of the slot is greater than 1 millimeter laterally from an edge of any of the plurality of nozzles to overcome boundary layer effects of air along the two inner sides of the slot, and a height between a highest point of the curved outer surface and the plurality of nozzles of the printhead is between 2.5 millimeters and 7.0 millimeters.

The printing device may include a pressure source input for pressurizing the printhead enclosure, the pressure source input configured and arranged to direct air from a pressure source to a component in the printhead enclosure that diffuses the air such that a uniform pressure distribution is provided throughout the printhead enclosure. The printhead enclosure is pressurized each time the printing apparatus is powered up so that the flow of air through the slot occurs both during printing and between prints. The features may include one or more of baffles, perforated plates, protrusions, nubs, or differently shaped objects designed to diffuse the air entering the printhead enclosure. The printhead may include: a print engine configured to selectively eject the liquid through the plurality of nozzles; a printer interface board coupled with the print engine; and a nozzle plate coupled with the print engine and defining at least a portion of the plurality of nozzles; the components can include components of the printer interface board coupled with the print engine.

The pressure source may comprise an air compressor providing shop air. The printing device may comprise the pressure source. The pressure source may comprise a blower. The pressure source may comprise a fan. The pressure source includes a pressure source assembly comprising: a filter; and an air intake device configured and arranged to prevent dust particles from entering the filter. And the printing apparatus may be included in a printing system comprising a controller apparatus including a user interface; and a print bar configured to receive two or more printheads of the printing device, the two or more printheads configured to be attached to the print bar and configured to be communicatively coupled with the controller device.

The printhead enclosure may include a pressure source located inside the printhead enclosure. The pressure source may be configured to cause air to enter the printhead enclosure through the filter located outside of the printhead enclosure. The pressure source is configured and arranged to direct air to one or more interior surfaces of the printhead enclosure that diffuse the air such that a uniform pressure distribution is provided throughout the printhead enclosure. The printing device may include a blower assembly. The blower assembly may include the filter located outside of the printhead enclosure. The blower assembly may include the pressure source.

Various embodiments of the subject matter described in this specification can be implemented to realize one or more of the following advantages. Factory dust particles can be prevented from entering the printhead enclosure and falling on the nozzle plate of the printhead. Satellite ink droplets and dust particles can be entrained in the air stream flowing out of the slot to prevent them from landing on the nozzle plate and clogging the nozzle. The effect of wood grain on the printed product due to the reorientation of ink drops and satellite drops by couette flow (due to the movement of the package/substrate past the print head) can be reduced or eliminated. The Total Cost of Ownership (TCO) for operating the printhead can be reduced by reducing ink waste due to purging, reducing or eliminating the use of purging operations (forcing a certain amount of ink through the nozzles to flush out dust and debris), and extending the life of the printhead. Preventing nozzle clogging can help extend the life of the printhead because nozzles that do not fire for long periods of time can overheat and damage the piezoelectric Transducer (PZT), and overheating can bake debris into the nozzles, making nozzle recovery more difficult and requiring more purging operations. Moreover, the described systems and techniques can help increase the throw distance between the nozzle plate and the substrate.

The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the invention will become apparent from the description, the drawings, and the claims.

Drawings

FIG. 1A illustrates one example of a printing system;

FIG. 1B illustrates one example of a printhead that may be used in the printing system of FIG. 1A or other suitable printing system;

FIG. 1C shows a rear side view of the printhead of FIG. 1B;

FIG. 1D shows an exploded view of a portion of the printhead of FIG. 1B;

FIG. 1E shows a partially exploded view of the printhead of FIG. 1B;

FIG. 1F shows a partial cross-sectional view of the fan assembly;

FIG. 1G illustrates a partially exploded view of another example of a printhead that may be used in the printing system of FIG. 1A or other suitable printing system;

FIGS. 1H and 1I illustrate exploded perspective views of examples of blower assemblies;

FIG. 2A is a cross-sectional view of a conventional inkjet printhead relative to a substrate;

fig. 2B is a cross-sectional view of an example of an inkjet printhead according to the present disclosure;

fig. 2C is a cross-sectional view of another example of an inkjet printhead according to the present disclosure;

3A-3F illustrate examples of slot shapes that may be used with a printhead enclosure according to the present disclosure;

4A-4B illustrate exploded views of examples of printheads that may be used in the printing system of FIG. 4A or other suitable printing systems;

FIG. 4C illustrates a perspective view of a lower portion of the printhead enclosure of FIG. 4A;

FIG. 4D illustrates a cross-sectional view of a lower portion of the printhead enclosure of FIG. 4A;

4E-4F illustrate cross-sectional views of an exemplary separator piece including a slot and an inclined surface;

FIG. 5A illustrates an example of a front portion of another printhead enclosure that may be used in a printhead in the printing system of FIG. 1A or in other suitable printing systems;

FIG. 5B shows a cross-sectional side view of a printhead having a front portion of the printhead enclosure of FIG. 5A;

FIGS. 5C and 5D show perspective views of the printhead of FIG. 5B with and without a cup to capture ink present in the printhead enclosure;

5E-5G show additional cross-sectional views of the printhead of FIG. 5B;

6A-6D illustrate examples of drip edge projections;

FIG. 7A illustrates a perspective view (with transparency) of another example of a printhead that may be used in the printing system of FIG. 1A or other suitable printing system; and

fig. 7B shows an exploded view of the printhead of fig. 7A.

Like reference numbers and designations in the various drawings indicate like elements.

Detailed Description

Fig. 1A illustrates an example of a printing system 100. The printing system 100 includes a cabinet 102 for housing a controller device having a user interface 104, and a (head) ink reservoir having a door 106 for access thereto. The printing system 100 also includes a print bar 108 configured to receive one, two, three, four, five, or more printheads 110. The print heads 110 may be repositioned and/or reoriented on the print bar 108 relative to one or more substrates to cause the print heads 110 to eject ink (controlled by the controller device of the printing system 100) to print an image on the substrate as the image moves past the print heads 110. In some embodiments, the print bar 108 is a print head carriage on its own roller, wheel or caster, allowing the print head carriage 108 to move independently of the chassis 102 that includes its own roller, wheel or caster. Further, it is noted that as used herein, a "substrate" for printing need not be a continuous substrate, but rather includes discrete packages and products, e.g., which move past the print head 110 on a conveyor in a production and/or packaging line.

The printed image may include alphabetic and/or numeric characters such as a date code or text serial number, bar code information such as one or two dimensional bar codes, graphics, logos (logos), and the like. The controller device (not shown) includes electronics that may include one or more processors that execute instructions (e.g., stored in memory in the electronic device) to control the operation of the printing system 100. Suitable processors include, but are not limited to, microprocessors, Digital Signal Processors (DSPs), microcontrollers, integrated circuits, Application Specific Integrated Circuits (ASICs), arrays of logic gates, and switch arrays. The electronics may also include one or more memories for storing instructions to be executed by the one or more processors and/or for storing data generated during operation of the printing system 100. Suitable memory includes, but is not limited to, Random Access Memory (RAM), flash RAM, and electronic read-only memory (e.g., ROM, EPROM, or EEPROM).

The substrate may be a label added to the product, the packaging material of the product (before or after the product is placed in the package) and/or the surface of the product itself. For example, the substrate may be a corrugated box containing one or more products. Thus, the print head 110 may be repositioned and/or reoriented on the print bar 108 relative to one or more product lines (including conveyors and/or other product movement mechanisms) that move the product through the facility. The facility may be a product manufacturing facility, a product distribution facility, and/or other industrial/commercial facility/building, and the product line may include a product packaging system, a product classification system, and/or other product handling/management system. It should be understood that printing system 100 is merely one example, and that many other suitable configurations may be used to construct a printing system that employs the printhead systems and techniques described herein.

Fig. 1B illustrates an example of a printhead 120 that may be used in the printing system 100 of fig. 1A as one or more printheads 110, or in other suitable printing systems. The printhead 120 includes a fan assembly 124 (e.g., a DC axial fan/blower) connected to the printhead enclosure, the fan assembly having a rear 126 and a front 138 connected to form an interior space within the printhead 120. The interior air space is pressurized by operation of the fan assembly 124, and the fan assembly 124 blows air from the external environment into the interior air space of the printhead 120. This air then exits the printhead enclosure through the slot 122 in the front portion 138 due to the pressure differential. As described in further detail below, the positive air pressure may prevent dust from entering the printhead enclosure, thereby preventing dust from falling on the nozzle plate.

FIG. 1C shows a back side view of the printhead 120 of FIG. 1B. The rear 126 of the printhead enclosure provides an opening through which an input/output interface 128 for the printhead 120 protrudes while maintaining a pressurized interior air space. These input/output interfaces 128 may include: an ink line interface for receiving ink (e.g., from an ink reservoir in chassis 102); a low vacuum interface to receive a first vacuum level to prevent ink from seeping from the printhead 120 by gently sucking ink in an ink reservoir in the printhead, and a high vacuum interface to receive a second vacuum level to draw air from the ink through a semi-permeable material in the printhead 120. It is noted that some implementations use the fan assembly 124 to push air into the interior air space of the printhead 120, as described further below, and other implementations use an input line (e.g., from shop air) connected to one of the interfaces 128 to pressurize the interior space of the printhead 120.

Additional interfaces 128 to the print head 120 may also be used. These may include user interfaces such as an eject test button and an ink purge button. These may also include one or more electronic interfaces to connect with control electronics within the printhead 120. The control electronics may include one or more processors that execute instructions (e.g., stored in memory of the control electronics) to control the print operating head 120. Suitable processors include, but are not limited to, microprocessors, DSPs, microcontrollers, integrated circuits, ASICs, logic gate arrays, and switch arrays. The control electronics may also include one or more memories for storing instructions to be executed by the one or more processors and/or for storing data generated during operation of the printhead 120. Suitable memory includes, but is not limited to, RAM, flash RAM, and electronic read-only memory (e.g., ROM, EPROM, or EEPROM).

In some embodiments, the electronics of the printhead 120 are divided between two components connected to each other, which provides flexibility for upgrades. FIG. 1D shows an exploded view of a portion of the printhead 120 of FIG. 1B. The control electronics are divided between the print engine 130 and the print interface circuit board 136. The print engine 130 includes a nozzle plate 132, the nozzle plate 132 having nozzles 134 through which the print engine 130 selectively ejects ink to form an image. The print engine 130 and the print interface circuit board 136 are coupled together to form the internal structure of the printhead 120.

In some embodiments, the electronics of the printhead 120 are split into two components that are connected to each other, which provides flexibility for upgrades. FIG. 1D shows an exploded view of a portion of the printhead 120 of FIG. 1B. The control electronics are divided into a print engine 130 and a print interface circuit board 136. The print engine 130 includes a nozzle plate 132 having nozzles 134 through which the print engine 130 selectively ejects ink to form an image. The print engine 130 and the print interface circuit board 136 are coupled together to form the internal structure of the printhead 120.

FIG. 1E shows a partially exploded view of the printhead of FIG. 1B. As shown, the print engine 130 and the print interface circuit board 136 are connected together and attached to the rear 126 of the printhead enclosure. The front 138 of the printhead enclosure is offset from the other components to illustrate how air flows past the printheads when the front 138 of the printhead enclosure is attached to the rear 126. The fan assembly 124 draws air 140 from the environment and pushes air 142 into the interior air space of the printhead. Air 144 passes in front of the nozzles 134 in the nozzle plate 132 and air 146 then exits the printhead through the slots 122. Note that the airflow through the slots 122 (and other example slots described throughout this application) may occur at all times when the printer is powered up to ensure that dust does not fall onto the panel between the printing plates, as well as during printing.

Fig. 1F shows a partial cross-sectional view of the fan assembly 124. The fan mounting portion 150 includes a fan, and the filter 152 filters dust particles from air blown into the print head 120. In addition, the fan assembly 124 may include features 154 at the air inlet to reduce the chance of dust particles entering the air stream before entering the filter 152. The features 154 may include louvers or angled fins of various shapes and sizes that may define a tortuous path (or be bent or rotated) and placed at the air intake to reduce the chance of dust particles entering the air stream before entering the filter 152. It should be appreciated that various types of fan assemblies and various internal configurations are possible for printheads constructed in accordance with the systems and techniques described herein, such as the blower assemblies described below in connection with fig. 1H and 1I. Typically, the printhead enclosure will be configured to contain a pressurized air space at least in front of the nozzles 134 of the printhead, and the slots 122 will be aligned with the nozzles 134 to allow selectively ejected ink to pass through the slots 122.

However, it should be noted whether an on-board pressure source (e.g., fan assembly or blower assembly 124) or an external pressure source (e.g., shop air from an air compressor provided through interface 128) is used, that the diffusion of air, ensuring even distribution of pressure from the printhead enclosure internal pressure source, is an important factor in maintaining good print quality with high gas flow rates through the slots. To address this issue, the internal structure in the printhead 120 should provide enough obstructions to diffuse the flow path of air from the pressure source so that the air flow is uniform around all sides of the nozzle plate 132.

The air may be diffused by deflection at multiple surfaces within the printhead 120, which may include components of the print interface circuit board 136. For example, as shown in FIG. 1E, the air flow input to the printhead 120 (either from the fan assembly 124 or from shop air input) may be input into the printhead enclosure from the side, rather than from the back, and then impact existing components on the print interface circuit board 136. However, direct input (from the side, back, or other direction) is not critical. In contrast, the air effect has a significant effect on the components within the print head enclosure. In some embodiments, the components include one or more of baffles, perforated plates, protrusions, nubs, and/or differently shaped objects designed to diffuse air entering the printhead enclosure to equalize the pressure level throughout the printhead enclosure, thereby homogenizing the airflow distribution of air flowing out of the slots. For example, the internal air diffuser may be designed based on the particular pressure source used and how air enters the printhead enclosure.

This configuration is advantageous for maintaining jet straightness even though the pressure level and the outflow volume are significantly increased. Thus, the use of a diffused airflow configuration allows for a substantial increase in air flow rate without adversely affecting print quality, since at higher air flow rates the velocity profile of the nozzle plate is more uniform over its entire length. In other words, the printhead enclosure is pressurized without a direct velocity path introducing air between the inlet and the slot 122, thereby providing a uniform velocity profile across the nozzle plate.

Additionally, as described in further detail below, the slot 122 may have various shapes and sizes. In some embodiments, the slot 122 is integrally formed with the printhead enclosure, e.g., using injection molding techniques, the slot 122 is formed simultaneously with the front portion 138 of the printhead. In some implementations, the slot 122 is added to the printhead enclosure as a separate component. The separate component may comprise a slider or hinge mechanism for opening the front of the enclosure to access the nozzle plate. A small purge may be necessary after a cold start to remove air from the ink channel behind the nozzles and to ensure that all nozzles are firing. In this case, this would facilitate opening the front of the enclosure to wipe away the purged ink.

FIG. 1G illustrates a partially exploded view of another example of a printhead 180 that may be used in the printing system of FIG. 1A or other suitable printing system. The printhead 180 can include various components described herein, including a print engine 130 having a nozzle plate 132, a print interface circuit board 136, and a fan assembly 124. However, the slot 122 is not integrally formed with the front 188 of the printhead enclosure. But rather in a separate component 182 which may include a sliding or hinge mechanism for opening the front of the enclosure to access the nozzle plate 132. In the example shown, the separate member 182 slides into and out of a receiving slot in the front 188 portion of the printhead enclosure.

This design allows the slot 122 to slide out if cleaning is required and the user needs to allow the cleaned ink to not accumulate within the printhead enclosure. It also allows the user to wipe ink from the nozzle plate 132. Note that it is often recommended to purge at machine start-up to remove air that may be trapped in the printhead due to thermal expansion and contraction. Other mechanisms for purging ink to be purged from within the printhead enclosure are possible, such as a slide out catch tray for purged ink, or the purge processing systems and techniques described in conjunction with fig. 4A-7B. Other variations are possible, such as replacing the fan assembly 124 with the blower assembly 440 of fig. 4A.

Fig. 1H and 1I illustrate exploded perspective views of a blower assembly 440 that may be used with any of the pressurized printhead enclosure embodiments described in this application. The blower assembly 440 includes a blower intake housing 441, which may be constructed of two identical parts assembled together as shown. The blower intake housing 441 includes an intake port 441A, a louver 441B, and a filter chamber 441C. The louvers 441B reduce the chance of dust particles from reaching the filter 442 contained in the filter chamber 441C when the blower intake housing 441 is brought together. The intake housing 441 is attached to the blower housing 444 by screws 447, and a gasket 443 is coupled between the intake housing 441 and the blower housing 444.

The gasket 443 may be placed inside the printhead enclosure wall (e.g., the inner surface of the rear portion 443 of the printhead 400 as shown in fig. 4B), which will help ensure that no air that does not first pass through the filter 442 enters the printhead enclosure. For example, the construction of filters is available from model P15/500S from Freudenberg Filtration Technologies, Germany and Carl Freudenberg KG. The blower housing 444 may also include a spacer 445, which spacer 445 retains the blower 446 within the blower housing 444 with screws 448. Note that blower 446, for example, part number KDB0305HA3-00C1J, available from Taida electronics, Taiwan, draws air from either side (both sides of blower 446 face the interior cavity of blower housing 444) and pushes the air into the interior of the printhead enclosure through air outlet 449.

Referring to fig. 4B, when blower assembly 440 is used with printhead 400 (described below with reference to fig. 4A), blower 446 pushes air against the inner surface of removable top 460 of the printhead enclosure. The inner surface of the removable top 460 is capable of diffusing air to provide a uniform pressure distribution throughout the printhead enclosure of the printhead 400. The embodiment of fig. 4A-4B may reduce and/or eliminate the need to remove the connection of blower 446 (which may be fragile in some cases) when disassembling the printhead enclosure to perform maintenance. The configuration of blower assembly 440 in fig. 4A-4B may also simplify maintenance of filter 442, as access to filter 442 may only require removal of air intake housing 441 from back plate 430. Although the blower assembly 440 is described in fig. 4A-4B as being used with the printhead 400, in some embodiments, the configuration of the blower assembly 440 is shown to be used with other printheads described in this specification, such as the printhead 180 previously described with reference to fig. 1G.

Fig. 2A is a cross-sectional view of a conventional inkjet printhead relative to a substrate 200. The printhead includes a nozzle plate 210 having an orifice 212 through which ink drops are ejected. In this example, there are two orifices 212 per nozzle to provide double the amount of ink, but in some embodiments there is only one orifice per nozzle, and in some embodiments there are more than two orifices per nozzle. Also, there are multiple nozzles (into the page) on the nozzle plate 210, but only one nozzle is shown in this cross-section. The nozzle plate 210 is covered by the housing 214 of the printhead and is also covered by a shroud 216 immediately to either side of the jets 212.

During printing, the substrate 200 is moved, for example, at a rate of 0.62 meters per second, as indicated by the arrows in fig. 2A. Note that the ejection frequency may be changed according to the speed of the substrate 200 so as to change the print resolution of horizontal Dots Per Inch (DPI). DPI in the horizontal direction (selecting the same data multiple times to increase DPI is called print density) is limited by substrate speed and firing frequency, since DPI is determined by the number of times you can gate the piezoelectric actuator that fires the ink drop. There is a frequency gating limit where increasing print density requires a reduction in the speed of the substrate 200. In addition, vertical DPIs are always the same, since this is a fixed distance between the holes of each nozzle, e.g. 200 DPI.

In any case, movement of the substrate 200 past the print head creates an air flow 205 between the two surfaces. This air flow 205 is known as couette flow, which is the flow of a viscous fluid (air in this case) in the space between two surfaces, one of which moves tangentially relative to the other. The gas flow 205 is driven by means of viscous drag acting on the fluid, but may also be additionally excited by a pressure gradient applied in the flow direction.

When an ink drop 220 is ejected from the printhead, the velocity of the ejected drop (e.g., 8 meters per second) entrains surrounding air through the drop drag and creates an air flow perpendicular to the couette flow. The interaction of this second air flow with the couette flow caused by the substrate movement creates a very small vortex, as indicated by the arrow curved to the right in fig. 2A. These vortices can create an unstable flow between the nozzle plate and the moving substrate, which can cause misdirection of the jet and produce wood grain defects in the print. When printing a plurality of ink droplets parallel to each other, a wood grain defect occurs, and the nozzle is bent due to an unstable flow field (swirl flow), thereby leaving an image that looks like wood grain, rather than individual parallel lines.

These vortices also redirect the ink satellites back to the nozzle plate 210. Note that when ink droplets are ejected from the orifices, satellites are formed in the course of the ink droplets naturally forming. It is a narrow portion before the ink drop breaks off from the orifice. When a drop breaks, the tail of the drop can detach from the drop body, causing the drop to become smaller (called a "satellite") in close proximity to the drop body.

These satellites may lose velocity and accumulate on the nozzle plate or may be redirected back to the nozzle plate 212 due to eddy currents. Over time, the satellites may completely block or reduce the ejection orifices that produce ink droplets that result in a jetted or bent ink jet.

Fig. 2B is a cross-sectional view of an inkjet printhead according to an example of the present disclosure. The printhead includes a nozzle plate 210 having an orifice 212 through which ink drops are ejected. In this example, there are two orifices 212 per nozzle to provide double the amount of ink, but in some embodiments there is only one orifice per nozzle, and in some embodiments there are more than two orifices per nozzle. Also, there are multiple nozzles (into the page) in the nozzle plate 210 cross-section, but only one nozzle is shown in this cross-section. The nozzle plate 210 is separated from the enclosure 230 of the printhead, forming an air space 235 between the nozzle plate 210 and the enclosure 230. As described above, the air space 235 is pressurized, resulting in an air flow 240 between the nozzle plate 210 and the enclosure 230. The air stream 240 passes through the slot 245 in the same direction as ink drops ejected from the apertures 212 in the nozzle plate 210.

Two problems are solved when the printhead jets an air stream containing ink drops (not shown) through the slot 245. First, the air flow prevents dust in the environment outside the printhead from reaching the nozzle plate 210, where it can build up over time and degrade print quality. Secondly, this air flow carries away the satellites and prevents the satellites from recirculating back and building up on the nozzle plate and preventing the wood grain effect due to the unsteady flow created by the vortex. These will have a positive impact on ink jet performance and print quality. By adding a positive air flow between the nozzle plate 210 and the front enclosure 230, it exits the slot 245 at the same exit point as the ejected ink, thereby preventing contaminants from the environment from being drawn into the printhead and falling onto the nozzle plate 210. In some embodiments, the positive airflow is set at a rate of 1 liter per minute to 28 liters per minute using the flat slot configuration shown in fig. 2B. For example, a minimum of 1 liter per minute prevents external environmental contaminants from entering the interior of the enclosure 230, and a minimum of 7 liters per minute overcomes the couette flow and prevents eddy currents that cause wood grain defects and redirection of the ink satellites toward the nozzle plate. Other air flow rates and ranges are also possible, such as 1-30 liters per minute and 7-30 liters per minute.

The creation of a positive pressure by the printhead around the ejected ink can effect a reduction or elimination of satellites build up on the nozzle plate 210 by overcoming or eliminating couette flow and bringing the satellites into the air flow through the slots and removing them from the area of the nozzle plate. The slot design can create an even air flow distribution in the gap between the slot 245 and the substrate 200, entraining ink satellites and dust particles into the air flow, directing them away from the nozzle plate, and preventing dust and ink from accumulating around the slot 245 opening. In addition, air flowing out of the slot 245 can assist the ink drop trajectory without affecting print quality.

In some embodiments, in order for the air flow to be effective for satellite problems, the positive air flow rate should be equal to or greater than the substrate velocity flow rate. That is, there is a limit to the flow rate that can be achieved and maintained effectively for satellite elimination. As the airflow increases, the mismatch in flow rates between the left and right sides of the nozzle plate is exacerbated. This can result in non-uniform airflow along the slot 245 and misdirection of the ejected ink drops, resulting in poor print quality. To address this issue, better diffusion of the air flow within the printhead should be ensured, for example, for flow rates greater than 19 liters per minute up to 30 liters per minute, the diffusion flow configuration is preferred over the direct flow configuration.

Fig. 2C is a cross-sectional view of another example inkjet printhead according to the present disclosure. As shown, the enclosure 260 of the printhead includes a shaped outer member 265 for the slot 245. The shaped outer member 265 affects the interaction of the couette flow with the air flow 240 exiting the slot 245. Adding curve 265 to the leading and trailing edges of the opening of slot 245 helps to reduce the flow rate (e.g., 7-15 liters/minute) because it directs the external air flow of the printhead enclosure to bend 270 from the slots on both sides. With the configuration shown in fig. 2C, the airflow 240 out of the slot 245 can reach at least 28 liters per minute in a diffuse airflow configuration and still reduce or eliminate satellites and dust from reaching the nozzle plate 210. Note that, in general, the velocity of the air flow out of the slot 245 should be greater than or equal to the velocity of the substrate 200. By modifying the shape of the slots 245, particularly the outer shape around the slots 245, couette flow can be mitigated to maximize filter life even at lower air flow rates (e.g., 7-15 liters/minute).

3A-3F illustrate examples of slot shapes that may be used with a printhead enclosure according to the present disclosure. In each of these examples, positive air pressure is created in the printhead enclosure (as described above) to push air through the slot in the same direction as the ink drops are ejected. The air flow from the printhead means that no shield is required on the nozzle plate. Note that this pressure level is external to the print engine and is different from the pressure levels used inside the print engine (e.g., low vacuum for preventing bleeding from the print head and high vacuum for drawing air out of the ink).

FIG. 3A is a cross-section of a slot shape 310 formed in an enclosure 302 of a printhead relative to a nozzle plate 300 having an orifice through which ink drops are ejected; as previously described, two orifices are shown per nozzle (to provide twice the amount of ink), but there may be one orifice per nozzle, or there may be more than two orifices per nozzle. The geometry of the slot 310 is a straight extrusion for the air flow. This geometry will prevent dust from the factory from entering the enclosure, but may require a higher minimum airflow requirement to overcome/counteract a given couette flow caused by substrate movement.

The slot shape 310 corresponds to the shape shown in fig. 2B. It has a flat outer surface 312 proximate the slot and a flat inner surface 314 of the slot itself. While the length of the slot (distance into the page) generally depends on the length of the array of orifices in the nozzle plate 300 (i.e., the number and spacing of nozzles in the print engine), various embodiments of the present disclosure may employ (1) different thicknesses of the enclosure 302, which may affect the height of the slot (left-right distance in fig. 3A), (2) different slot widths that affect the air flow rate through the slot (up-down distance in fig. 3A), and/or (3) different distances between the inner surface of the enclosure 302 and the exterior of the nozzle plate 300, which may affect the air flow pattern as air is pushed into and through the slot.

Fig. 3B is a cross-section of a slot shape 320 formed in the enclosure 302 of the printhead relative to the nozzle plate 300. In this example, the thickness of the enclosure 302 is not changed, but the leading and trailing edge surfaces of the slot have been modified. Specifically, a curve 322 has been added to create a smooth transition from the outer surface of the printhead enclosure 302 to a flat portion 324 of the inner surface of the slot. The slots 320 have a diverging slot geometry with an inlet area that is much smaller than an outlet area. This can create a pressure differential over the length of the slot, especially at higher flow rates (about 30 liters/min), and a low pressure region at the exit region of the slot, which can attract dust particles to the slot opening. In addition, pressure differences along the length of the slot can affect the trajectory of the ejected ink drops, which in turn can affect print quality.

Furthermore, the diverging profile causes turbulence in the velocity profile along the length of the slot, which prevents an even distribution of the air flow between the enclosure and the substrate, which is undesirable. Similarly, a converging slot interior (an inversion of the slot shape 320, where the exit area is much smaller than the entrance area) can create high velocity areas at the top and bottom areas of the slot opening, resulting in fluid recirculation. In these regions, the slot exit velocity is high enough to overcome the couette flow caused by the substrate motion, but the converging profile also creates turbulence in the velocity profile along the length of the slot, which prevents even distribution of flow between the enclosure and the substrate. The particular shape of the slot is therefore a key factor in making the system effective, as slot shapes that create air turbulence or mismatch may be less effective in preventing satellites from reaching the nozzle plate and may negatively impact print quality.

Fig. 3C is a cross-section of a slot 330 formed in the enclosure 304 of the printhead relative to the nozzle plate 300. As shown, the enclosure 304 is thinner than the enclosure 302, and an outer shape 332 has been added to the slot 330. This can both increase the height of the slot 330 and overcome/counteract the couette flow generated by the moving substrate. The geometry of the slot (with straight air passages and curvature on the outside) causes high velocity air to flow out of the slot opening, entraining ambient air particles which follow the shape of the outer curvature. For air flow rates greater than 7 liters per minute, the slot design 330 determines the flow field by counteracting the couette flow effect of moving substrate. For an airflow rate of 10 liters per minute, this slot geometry may produce a near perfect flow separation curve, successfully deflecting dust particles away from the spray array. Secondary recirculation zones observed near the top and bottom of the slot opening are far from the region of interest.

The slot shape 330 corresponds to the shape shown in fig. 2C, but further modifications to the shape and size of the slot 330 are possible while still having a profile that prevents couette flow (created by movement of the substrate) from sweeping the factory air in front of the slot. Fig. 3D shows a slot 340 formed in the housing 306 of the printhead relative to the nozzle plate 300. As shown, the outer shape of the slot 340 includes a first curve 342 and a second curve 344. Both of these curves may improve the functionality of the nozzle and make the slot 340 easier to manufacture. In some embodiments, the slot 340 has a first curve 342 with a radius of curvature of 1.5mm, an inner width 346A (slot opening) of 3.0mm, an outer width 346B of 4.0mm, a height 348A of 2.0mm, and a height 348B from the nozzle plate 300 of 3.5 mm. These dimensions are suitable for use in conventional Drop On Demand (DOD) inkjet print engines and can be modified as the size of the inkjet array changes. Additionally, these dimensions may vary in different implementations, but suffer from the following problems.

As the width 346B becomes larger, for example, greater than 5.0mm, there is a risk that the leading edge of the slot is too far from the airflow exiting the slot so that it no longer creates sufficient resistance to affect couette flow. Also, the slot opening 346A should be wide enough so that the ejected droplets have enough clearance not to contact the side walls of the slot. In the depicted example, the width of the inkjet nozzles on the nozzle plate 300 is 0.5mm, so the openings 346A should provide a margin on either side that allows for at least 1.25mm of cushioning. If opening 346A is too small, ink can accumulate and affect the airflow. In some cases, the slot channel width 346A should be at least 2.7mm to overcome the boundary layer effect of the slot walls on the airflow. Further, increasing the slot width 346A may decrease the slot exit velocity, which may result in undesirable vortex flow.

The

height

348A, 348B of the slot is based on the maximum throw distance of the jetting technique. In this example, the throw distance of the hot melt ink jet printer is at most 8 millimeters (other throw distances are possible). Any throw distance beyond this distance means that the jet begins to fall before hitting its intended target area, leading to print quality problems. The dimensions provided above allow the slot shape to redirect the couette flow and also have some clearance between the slot and the substrate. It also allows air to pass through a 1mm gap between the nozzle plate 300 and the inner surface of the housing 306 (e.g., the front cover of the printhead) before passing through the slot opening.

The slot radius 342 may vary, limited by the slot height 348A, and in some cases, the slot radius 342 should be less than or equal to 2.0 mm. For radii of up to 2.0mm, the curvature of the slot geometry directs the air flow evenly to both sides of the slot opening and successfully cancels the couette flow effect from the moving substrate. For radii greater than 2.0mm, the curvature may not be sufficient to promote uniform flow distribution on both sides of the slot opening. The couette flow effect of substrate movement becomes more pronounced as the slot radius increases. In addition, the slot length can be increased without affecting printing performance. However, it is generally preferred to limit the slot length to comfortably enclose the top and bottom jets without further lengthening, since as the slot length increases, the average slot air outlet velocity decreases as the amount of intake air entering the print head decreases.

Thus, in some embodiments, a slot shape with a straight internal channel and a curved outer surface is used, as shown in fig. 3D. Slot radius 342 may be in the range of 1.0 to 2.0mm, inner width 346A may be in the range of 2.7 to 4mm, outer width 346B may be in the range of 4 to 5.0mm, height 348A may be in the range of 1.0 to 5.5mm, and height 348B may be in the range of 2.5 to 7.0 mm.

Additionally, it should be noted that reducing the distance between the front of the slot opening and the surface of the substrate on which printing is to be performed may improve performance, allowing for lower air flow rates and increased filter life. Typically, the distance should be less than or equal to 3.0 millimeters, less than or equal to 2.0 millimeters, or less than or equal to 1.0 millimeters. In some cases, the distance between the front of the slot opening 340 and the surface of the substrate and the slot geometry 340 is employed to be less than or equal to 1.0mm so that the couette flow effect can be overcome/counteracted with an air flow rate of 5 to 7 liters/minute.

Other slot shapes for the nozzles of the printhead are also possible. Figure 3E shows a slot 350 for an ink jet nozzle plate. FIG. 3F shows another slot 360 for an ink jet nozzle plate. Note that as shown, the slot shape 360 provides even further redirection of the couette flow, allowing the airflow to naturally turn back on both sides of the slot. However, the slot shape 360 can be challenging in the manufacturing process. The slots described in connection with fig. 3A-3F may be molded into the printhead enclosure or may be added after the printhead enclosure is initially constructed. The slots described in connection with fig. 3A-3F may be constructed using various manufacturing systems and techniques, including injection molding, Computer Numerical Control (CNC) milling, and three-dimensional (3D) printing. It should be noted, however, that the inner wall surfaces of the slots may be made smooth to promote a steady flow of air out of the slots (with as little turbulence as possible), and that certain 3D printing techniques may produce ribs or other undesirable protrusions on the inner surfaces of the slots. In some embodiments, when the slot is widened, a less smooth inner wall surface may be used in the slot to ensure that the air in which the ink droplets move has a laminar flow, i.e., a laminar flow passing through the center of the slot and in line with the ink droplets, so that any air turbulence along the inner wall of the slot does not affect the flight and placement of the ink droplets. 3A-3F are all mirror images of the leading and trailing edges, it should be understood that this is not required. In some embodiments, the shape of the leading edge of the slot is different from the shape of the trailing edge of the slot.

Generally, the profile of the slot is designed to help overcome/neutralize couette flow at lower gas flow rates (e.g., less than or equal to 10 liters/minute). This helps to maximize the life of the filter for intake air, as less air per unit time translates into less particulates captured by the filter per unit time.

Fig. 4A-4B illustrate exploded views of examples of a printhead 400 that may be used in the printing system 100 of fig. 1A as the printhead 110, or in other suitable printing systems. The printhead 400 includes a print engine 410 having a nozzle plate 412 and a print interface circuit board 414. The print interface circuit board 414 is an example of a circuit configured to selectively eject ink through a plurality of nozzles 418 in the nozzle plate 412 and through an opening 420 of the printhead enclosure to form an image on a moving substrate. The opening can be of various sizes and shapes, but should be in front of the nozzle 418, i.e., the opening 420 is located between the nozzle 418 and the substrate on which printing is to be performed, to allow selectively ejected ink to pass through the opening when the selectively ejected ink is ejected toward the moving substrate.

The nozzle plate 412 and print interface circuit board 414 can be identical to the corresponding nozzle plate and print interface circuit board components described in other embodiments of the present application, e.g., the nozzle plate 132 and circuit board 136 in fig. 1G. Additionally, the printhead 400 may (or may not) include other components of other embodiments of printheads described herein, such as a pressurized printhead enclosure having an on-board pressure source, such as a fan assembly or blower assembly 440, and/or an input line for an external pressure source (e.g., shop air). Thus, the opening in front of the nozzle 418 may be a slot 422 aligned with the plurality of nozzles 418. Slot 422 may be integral (integrally formed) with the printhead enclosure, such as slot 122 in fig. 1E; or the slot 422 may be integral (integrally formed) with a separate piece 424 of the printhead enclosure, such as separate piece 182 in fig. 1G, where the integral slot or movable slot may or may not include the slot designs described in detail in this specification. In addition, the printhead 400 includes a rear portion 430 of the printhead enclosure, which may be the same as the rear portion 126 in fig. 1C, and/or the printhead 400 may include other components.

In the example shown in fig. 4A, the print engine 410 also includes an ink reservoir 416 that can be filled from an ink input line that passes through an ink line interface of the rear portion 430, but in some implementations, the ink reservoir 416 is not included in the printhead 400, with ink being delivered directly from the ink input line to the ejection array 418. Note that some embodiments use liquid inks, which remain liquid at ambient temperature, while some embodiments use phase change inks (also referred to as hot melt inks), which are solid at ambient temperature but change to a liquid phase at elevated temperatures. In any case, circuitry in the printhead, such as the print interface circuit board 414, is designed to clear ink through the plurality of nozzles 418, according to program instructions, or in response to a user pressing a cleaning button on the printhead, or a combination of both. The printhead enclosure design may provide a small gap (e.g., 1mm) in front of the ejection array 418, which allows purged ink to drain by gravity (and heat if hot melt ink is used) into the bottom interior surface of the printhead enclosure. Thus, the printhead 400 includes features that facilitate removal of ink that is flushed, for example from the ink reservoir 416, through the nozzles 418 (in the nozzle plate 412) and into the interior of the printhead enclosure.

Note that purging is generally recommended at machine start-up to remove air that may be trapped in the jets due to thermal expansion and contraction, and may also be performed periodically during printhead operation. Also, different printheads will require different amounts and frequencies of cleaning depending on the type of ink and the rate of debris accumulation. For example, the use of a pressurized printhead enclosure as described herein may substantially reduce the accumulation of debris, resulting in a reduced need for purging and a reduced amount of ink during purging. However, in some embodiments, a larger amount of ink may be purged through the nozzle 418, and the exemplary embodiment shown in fig. 4A-4D is designed to handle a larger flow of ink during purging.

The purged ink flows (under the force of gravity) down the surface of the nozzle plate 412 and onto the inner surface of the bottom of the printhead enclosure for the printhead 400. As shown in fig. 4A, the printhead enclosure includes a separate top 460 and a separate bottom 470, where the bottom 470 is connected with the top 460, e.g., using a sliding or hinge mechanism, to form a front of the printhead enclosure, which is connected with a rear 430 of the printhead enclosure.

In the example shown, the bottom 470 includes a tab 472, the tab 472 sliding into and out of a receiving slot 462 in the top 460 of the printhead enclosure. FIG. 4C illustrates a perspective view of the lower portion 470 of the printhead enclosure of FIG. 4A. Fig. 4D shows a cross-sectional view of the lower portion 470 of the printhead enclosure of fig. 4A. However, these particular structures are not required. Other connection mechanisms may be used to connect the various portions of the printhead enclosure, nor is a three-part housing necessary.

In some embodiments, the top portion 460 and the bottom portion 470 are one-piece, such as described in further detail below. In some embodiments, bottom portion 470 and rear portion 430 are integral, forming the bottom of the printhead enclosure, but a portion of that portion is located at the top of the printhead. Other designs of two, three or more parts are possible. It is noted that all of these printhead enclosure portions, such as

printhead enclosure portions

424, 430, 460, 470, may be manufactured using plastic injection molding systems and techniques. In some cases, the separating member 424 is made of a different material, such as a metal. Additionally, it should be noted that "bottom" and "top" herein are with respect to a given print direction of the printhead, and that the printhead, when positioned relative to a substrate including a vertical direction, may have multiple print directions, including the vertical ejection position, horizontal ejection position, and downward ejection position shown in fig. 4A, and rotational variations thereof, such as a 45 degree angled position. In the downward firing direction, the individual components 424 may be removed for cleaning, so that purged ink may exit the printhead enclosure through the opening 120 rather than through the aperture 480.

However, in some embodiments, it may be advantageous to have a top portion of the printhead enclosure that is easily separable from a bottom portion of the printhead enclosure. Not all of the ink flows out of the printhead enclosure, and the use of separable top and bottom portions may facilitate cleaning and maintenance of the printhead. In particular, hot melt inks tend to solidify and adhere to the interior bottom of the printhead enclosure. For liquid ink, the bottom can remain in place as an ink tray, preventing ink from spilling when the printhead is turned on.

As the printhead cools, the hot melt ink solidifies and may seal the printhead enclosure to one or more other components within the printhead (e.g., ink tank 416), making it difficult to disassemble the printhead for cleaning and maintenance. Using a design with a separate top piece 460 allows the top piece to be easily removed, such as by sliding off in the example shown, so that the print engine 410 and its components can be easily accessed for servicing even if hot melt ink freezes a portion of the print head 410 of the print engine 410 to a portion of the bottom of the print head enclosure. However, due to the use of heating elements, as described in further detail below, upon heating, ink will be allowed to drain from the printhead over time, and the amount of hot melt ink within the printhead enclosure will not be high enough to contact the top 460 and prevent the top 460 from being removed for servicing.

Whether liquid ink or phase change ink is used, the inner bottom surface of the printhead enclosure may be open to a channel 490, wherein the channel 490 is angled with respect to the horizontal plane of the print direction of the printhead, such that purged ink flows through the channel 490 to the orifice 480. Thus, the upper end 492 of the channel 490 is located below the nozzle 418, the lower end 494 is located at the aperture 480, and the printhead enclosure is configured to direct ink to the aperture 480 such that the ink flows out of the printhead enclosure via the aperture.

Note that although the aperture 480 is shown as circular, many different shapes are possible, including oval, square, rectangular, hexagonal, etc. In addition, the slope of the channel 490 and the slope of the leading purged ink to the bottom surface of the bore 480 can vary widely. The angle of the surface may be 1 degree or other angles as long as the angle is steep enough to allow the ink to flow to the orifice 480 under the force of gravity. For example, for certain types of ink, the angle may be less than one degree, such as between 0.25 degrees and 1 degree. Larger angles are also possible, for example, angles between 1 and 5 degrees (inclusive), angles between 1 and 10 degrees (inclusive), angles between 1 and 15 degrees (inclusive), angles between 1 and 20 degrees (inclusive), angles between 1 and 25 degrees (inclusive), and angles between 1 and 30 degrees (inclusive).

Further, the channel 490 may be formed from or associated with various structural features that help direct purged ink in an appropriate manner. For example, one or more steps 490A and/or one or more sloped surfaces 490B (forming a sloped wedge) may be used to help direct ink into the channel 490. The side draft angle on surface 490B may be utilized to prevent ink from wicking (wick) onto the bottom surface of printhead array 418, and then a path of least resistance may be created to allow purged ink to drain under heated reservoir 416. The side draft angle may ensure minimal ink build up in the housing and allow the housing to be easily removed when the system is shut down.

Other shapes, such as one or more wedges in place of step 490A, may be used to form the channel 490. In embodiments employing phase change ink, these shapes may help direct ink to a component, such as a heating edge 452 of a heating wall 450 located along an interior surface of the printhead enclosure, which is heated to melt and flow the phase change ink on the interior surface of the printhead enclosure to the aperture 480. For example, the heating wall 450 may be a heating wall for the ink reservoir 416 that includes a portion 454 that extends beyond a bottom surface of the ink reservoir 416. The use of extended heating walls of the ink reservoir 416 has the advantage of keeping the cost of the printhead low, since no additional components need to be added to the printhead; the same heater (not shown) that heats the reservoir wall 450 also provides heat to keep the hot melt ink flowing to the orifice 480. However, if two different temperatures are desired, other heating elements may be used to heat the ink, such as a separate metal structure coupled to a heater for ink container 416 or to its own heater.

Regardless of which type of structure is used as the heating element, the heating element is positioned along the interior surface of the printhead enclosure and is spaced from the interior surface of the printhead enclosure by a distance that is sufficiently small (as determined by the phase change ink) that, when the element is heated, the phase change ink will remain molten under the element along the path to the orifice. In some embodiments, the heating element also includes a portion, such as portion 456, that extends into aperture 480 to ensure that the phase change ink remains in a molten state as it passes through aperture 480.

In addition, the orifice 480 is preferably well spaced from the nozzle plate 412 to allow ink to exit the printhead 400 at a relatively remote location from the substrate, i.e., the orifice 480 is spaced from the production or packaging line. In some embodiments, the aperture 480 is located in a back half of the printhead enclosure opposite the opening 420. In some embodiments, the aperture 480 is located in the rear quarter of the printhead enclosure opposite the opening 420, as shown in FIG. 4C. In some embodiments, the holes 480 are disposed as close to the rear edge of the back 430 as possible. Note that keeping the drip openings 480 away from the front of the print head 400 facilitates placing the print head 400 further above and as far down as possible from components of the production and/or packaging line (e.g., a conveyor belt).

Furthermore, although the described channel 490 structure need not be used with a separately removable top 460 of a printhead enclosure, as shown in fig. 4A-4D, using such a two-part (or three-part or more) design for a printhead enclosure that includes the channel 490 may be advantageous for manufacturing purposes because manufacturing a one-part design for a front of a printhead enclosure that includes such additional structural shapes may be challenging due to manufacturing limitations of manufacturing components by injection molding processes. Additionally, in some embodiments, even if a defined shape is not added to the printhead enclosure to create the channel 490, the channel may still be effectively formed, and thus a single front piece may be readily used with the printhead enclosure.

Fig. 4E-4F illustrate cross-sectional views of an exemplary separator 824, the separator 824 including a slot 822 and an angled surface. As shown, the separator 824 includes a first section 824a and a second section 824b, the first section 824a and the second section 824b being proximate to the slot 822 and defining a boundary of the slot 822. The second piece 824B includes an inclined surface 824B' extending from an edge of the slot 822 towards the nozzle plate 412 of the printhead 400 shown in fig. 4A-4B. The second piece 824b is shaped to direct the flow of purged ink 825 toward the bottom 470 of the printhead 400 and to prevent a build-up 825' of the purged ink 825 from exiting through the slot 822. While the second section 824b is shown in fig. 4E-4F to include a particular wedge shape, the second section 824b may be designed to form different types and sizes of angles, chamfers, radii, wedges, and/or slopes. In some embodiments, one or more features of the separator 824 (e.g., the sloped surface of the second portion 824B) are included in other separators described herein, such as the separator 424 previously described with reference to FIGS. 4A-4B, the separator 182 previously described with reference to FIG. 1G, and the separator 504 subsequently described with reference to FIG. 5A. in some embodiments in which the slot is integral with the printhead enclosure, the parts 824A, 824B may describe parts of the portion of the printhead enclosure proximate the slot, such as the top 460 previously described with reference to FIG. 4A, and the

front portions

138, 500 described with reference to FIGS. 1B and 5A. Thus, although the embodiments described with reference to fig. 4E-4F are illustrated as being used with the printhead 400 of fig. 4A-4B, in some embodiments, one or more features of the separator 824 are used with other printheads described herein.

Furthermore, although the embodiments shown in fig. 1 and 2 describe the second section 824b as being proximate to the shorter dimension edge of the slot 822, in some embodiments including a printhead in the horizontal ejection direction, the second section 824b may be proximate to the longer dimension edge of the slot 822. In embodiments including a printhead that can be used in both the vertical and horizontal ejection directions, the second part 824b can describe a part that is close to both: at least one longer dimension edge and at least one shorter dimension edge.

Fig. 5A illustrates another example of a front portion 500 of a printhead enclosure that may be used for a printhead in the printing system 100 of fig. 1A, as the printhead 110, or in other suitable printing systems. Front 500 includes an opening 502 that is integral (integrally molded) with a separate piece 504 of the printhead enclosure, e.g., the same as separate piece 424 in FIG. 4A or separate piece 182 in FIG. 1G. Additionally, front portion 500 includes an inner surface 510 that is flat (i.e., no channels are fabricated), but also angled with respect to the horizontal of the print orientation of the printhead to cause the phase-change ink to flow to orifice 520, e.g., the same as orifice 480.

Furthermore, although the embodiments shown in fig. 4E-4F describe the second portion 824b as being near the edge of the shorter dimension of the slot 822, in some embodiments, including the printhead in the horizontal ejection direction, the second portion 824b may be near the edge of the longer dimension of the slot 822. In embodiments including printheads that can be used in both the vertical and horizontal ejection directions, the second portion 824b can be described as a portion proximate to both the at least one longer dimension edge and the at least one shorter dimension edge.

Fig. 5A illustrates another example of a front portion 500 of a printhead enclosure that may be used for a printhead (printhead 110) in the printing system 100 of fig. 1A, or a printhead in other suitable printing systems. Front 500 includes an opening 502, opening 502 being integral (integrally molded) with a separate piece 504 of the printhead enclosure, e.g., the same as separate piece 424 in FIG. 4A or separate piece 182 in FIG. 1G. Additionally, front portion 500 includes an inner surface 510, inner surface 510 being flat (i.e., no channels are fabricated), but also angled with respect to a horizontal plane of the print direction of the printhead to cause the phase-change ink to flow to orifice 520, e.g., the same as orifice 480.

As shown, after the hot melt ink is purged, the front 500 of the printhead enclosure has been removed and a channel 512 is formed by an amount of phase change ink 514 that spreads out from the heating member along an interior surface 510 of the printhead enclosure and solidifies some distance away from the heating member. Note that this distance depends on the nature of the phase change ink and the amount of heat dissipated by the heating element. In any event, the phase change ink inside the enclosure, which is not adjacent to the heating surface, freezes, which creates an ink dam around the melted ink region, creating a natural channel along the outer edge of the heating region.

FIG. 5B shows a cross-sectional side view of a printhead 530 having a front 500 of the printhead enclosure of FIG. 5A. As shown, inner surface 510 is in close proximity to heating component 540, in this example, heating component 540 is an extension of heating wall 545 for the ink reservoir. The distance between inner surface 510 and the bottom edge of heating component 540 is small enough so that when the phase change ink melts, the phase change ink remains in contact with both heating wall 545 and inner surface 510 of printhead enclosure 510 along channel 512 until the phase change ink passes through aperture 520. Like the heating wall 450, the heating wall 545 may extend beyond the bottom surface of the ink reservoir to which the heating wall 545 is connected, and does not require as many extensions 540 to facilitate the use of the printhead enclosure to capture and remove purged ink from the printhead 530, thereby keeping the overall size of the printhead 530 small.

Further, the ink does not require a large angle 532 (relative to horizontal 534) to naturally flow (as melted) along the inner surface 510 under the force of gravity from the higher end 522 below the plurality of nozzles to the lower end 524 at the orifice 520. In this example, the angle 532 of the inner surface 510 of the printhead enclosure is an angle relative to a horizontal plane 534 of the print direction of the printhead 530. Other angles are possible as long as the angle is sufficiently steep to allow ink to flow toward the orifice 520 under the force of gravity. For example, for certain types of ink, the angle may be less than 1 degree, such as between 0.25 degrees and 1 degree. Larger angles are also possible, for example, angles between 1 and 5 degrees (including both ends), angles between 1 and 10 degrees (inclusive), angles between 1 and 15 degrees (inclusive), angles between 1 and 20 degrees (inclusive), angles between 1 and 25 degrees (inclusive), and angles between 1 and 30 degrees (inclusive). Further, in this example, the extended heating wall 545 is slightly sloped at its bottom to match the draft angle of the enclosure (e.g., 1 degree), so the extended heating wall 545 provides a trackable edge for the ink, i.e., the melted ink tends to wick along the edge of the extended wall 545. Thus, the dimensions of heating wall 545 relative to surface 510 ensure thermal contact between the ink and the edges of extended heating wall 545.

In addition, heating component 540 may include a portion 542 (e.g., similar to portion 456 in fig. 4A) that extends into aperture 520 to keep the phase change ink melted as it passes through aperture 520, and printhead 530 may include a holder 536 to hold a container to capture ink that passes through aperture 520. Fig. 5C and 5D show perspective views of the printhead 530 of fig. 5B, with and without cups 538 to capture ink exiting the printhead enclosure, respectively. Note that the location of the bracket 536 allows the cup 538 to be easily removed by sliding the cup 538 off the front of the print head 530, allowing the cup 538 to be replaced without disturbing items placed near the front of the print head 530, such as production and/or packaging line components (e.g., conveyor belts) or other components (e.g., umbilicals).

Additionally, the bracket 536 and cup 538 design is advantageous when used in conjunction with the pressurized printhead enclosure designs described in this application. The size of the apertures 520 may be small enough (and preferably small in the case of hot melt ink to ensure that the ink can remain heated and not solidify before exiting the printhead) so that the apertures do not interfere with the nozzle airflow required by the pressurized printhead enclosure design. In addition, a cup 538 located at the outer bottom of the enclosure is removably secured near the enclosure aperture using a bracket 536, which further prevents air leakage and affects the pressurized printhead enclosure.

In some embodiments, a small diameter cup 538 is used so that the hot melt ink flows to the edge of the cup before it freezes, and the entire volume of the cup can be filled before it needs to be replaced (determined by the characteristics of the phase change ink and the ambient temperature around the printhead). For example, the cup 538 may be a ready-to-use 3 ounce (89cc) cup (e.g., made of clear plastic to facilitate determining when the cup should be replaced). In other embodiments, a deeper receptacle (even if the diameter remains small) may be used to provide more time during cup replacement. In other cases, larger containers (e.g., pans or drums) may be placed on the floor or table below the ink outlet, thereby providing greater flexibility in the type of container used and the frequency of replacement.

In addition, a heated component (e.g., portion 542 of heating component 540 in FIG. 5B) may extend into aperture 520 to keep the phase change ink molten as it passes through aperture 520 and into cup 538. Fig. 5E shows a perspective cross-sectional view of the printhead 530 in fig. 5B. In this example, the portion 542 of the heating wall 545 for the ink reservoir extends partially into the aperture surrounded by a protrusion 550 disposed in the bottom side 580 of the printhead enclosure of the printhead 530 (in the printing direction), the protrusion 550 being located above the cup 538.

Fig. 5F shows a closer perspective cross-sectional view of the protrusion 550. As shown, the protrusion 550 is circular, has a lower surface 552, and has a width 554, but the protrusion 550 may have a different shape as the aperture itself. Note that there may be many variations in the protrusion and drip edge at the orifice, which are equally applicable to liquid ink, as described below, that do not require the heating portion 542 to keep the ink molten at the orifice. Typically, the protrusion at the aperture should extend far enough below (in the direction of printing) the outer bottom surface of the printhead enclosure to prevent ink from wicking onto the outer bottom surface of the enclosure and possibly spreading out from the protrusion at the bottom of the printhead. Furthermore, the drop edge of the protrusion should have a sufficiently small surface portion below the outer bottom surface of the printhead enclosure (in the printing direction) to allow gravity to overcome the surface tension of the ink on the surface portion of the protrusion (depending on the viscosity of the ink).

In the example shown in FIG. 5F, the protrusion 550 is located within a counterbore 560 in a bottom side 580 of the printhead enclosure of the printhead 530. The protrusion 550 includes a surface portion 552, and a width 554 of the surface portion 552 is sufficiently small (e.g., one millimeter) to create an effective drip edge, i.e., gravity overcomes the surface tension of the ink at the surface portion 552 of the protrusion 550. The protrusion 550 extends below the bottom surface 562 of the counterbore 560; surface 562 is also a bottom surface of printhead 530. The use of counterbore 560 provides an additional edge 564 to ensure that no ink reaches the major bottom surface 580 of the printhead enclosure of printhead 530. Thus, the counterbore 560 forms a pocket in the bottom side 580 of the printhead enclosure of the printhead 530 that completely surrounds the protrusion 550. This design may simplify the manufacturing process, thereby making the printhead enclosure easier to manufacture and less costly to produce.

Note that because of counterbore 560, protrusion 550 extends below bottom surface 562 of printhead 530, bottom surface 562 being at a different height than bottom surface 580. FIG. 5G shows a cross-section, primarily the side, of the protrusion 550 and counterbore 560 of FIG. 5F. As shown, the distance 570 between the heating element 540 and the inner surface of the bottom side 580 of the printhead enclosure is very small, e.g., 0.1-0.5 millimeters, which facilitates the flow of phase change ink inside the printhead 530. Further, some embodiments do not require any gap 570, and heating member 540 may be positioned such that it contacts the enclosure, thereby causing the molten ink to flow along the edge of heating member 540 into the aperture. A larger gap 570 is also possible because the hot melt ink may solidify at the bottom of the enclosure, while still forming a melt channel in the ink and continuing to direct the ink along the melt channel to the aperture 520.

The diameter 590 of the orifice 520 may be 5-9 mm, such as 7mm, and is sized to ensure that there is sufficient space for ink to leave the orifice and remain near the hot drop 542. The raised surface portion 552 extends, for example, 2 millimeters below the bottom surface 562, further beyond the edge 564 and below the major bottom surface 580 of the printhead enclosure. The use of the protrusion 550 in conjunction with the heating portion 542 ensures that the hot melt ink does not build up around the hole, cool and plug the hole.

Portion 542 of heating element 540 extends into the hole far enough to keep the phase change ink molten as it drips from drip edge 552. In the example shown, portion 542 of heating element 540 extends at least halfway into the hole. However, it should be understood that the size, location, and extent of the portion 542 can vary depending on the properties of the phase change ink. It is, however, preferred not to have portion 542 extend all the way through the hole and not beyond the bottom edge 552 of projection 550, as this may pose a risk of injury if someone places a finger over the hole. Accordingly, bottom edge 552 of protrusion 550 may extend at least one millimeter beyond the bottommost portion of heating tab 542 to isolate the hot drop from the exterior enclosure surface. Generally, portion 542 of heating member 540 is shaped and sized to direct phase change ink into the orifice and prevent ink droplets outside the orifice from freezing because a frozen droplet hanging in the orifice can block the orifice. The ink must remain molten until it passes completely through the orifice where gravity can pull the ink out of the orifice. Note that as shown, the shape and size of the portion 542 may serve as another drip edge, and therefore ink may drip from the portion 542 in addition to the drip edge 552. Further, as described herein, the portion or tab 542 may be sized to maintain a small gap between the portion/tab 542 and the inner surface of the aperture 520, thereby reducing the amount of air that may flow from the printhead if a pressurized printhead enclosure is used.

In addition, other designs of apertures, protrusions, and drip edges are possible with or without the use of phase change ink. Thus, as described above, the use of the projection and the drip edge does not require the heating member 540. In addition, variations of the edge 564 are also possible, including creating pockets that do not surround the protrusions.

Fig. 6A shows an example of a drip edge projection 600. The aperture 605 passes through a wall 610 of the printhead enclosure and the protrusion 600 has a lower edge 602, the lower edge 602 extending a distance 615 (e.g., 2 millimeters) beyond an outer bottom surface 612 of the enclosure wall 610 to ensure that ink passing through the aperture 605 (and dripping from the edge 602) does not wick back onto the outer surface 612. However, the protrusion need not actually protrude to increase the overall height of the printhead enclosure.

Fig. 6B shows another example of the drip edge projection 620. An aperture 625 passes through a wall 630 of the printhead enclosure, and the protrusion 620 has a lower edge 622, the lower edge 622 extending beyond an outer bottom surface 632 of the enclosure wall 630. But the lower edge 622 also extends beyond the outer bottom surface 634a distance 635 (e.g., extending 2 millimeters), the distance 635 being sufficient to ensure that ink passing through the aperture 625 (and dripping from the edge 622) does not wick back onto the outer surface 634. This is an example of a counterbore implementation where the lower edge 622 extends 1mm beyond the outer bottom surface 632 of the enclosure wall 630, e.g., the wall 630 has a thickness of 2 mm, the counterbore has a depth of 1mm, and the protrusion 620 has a length of 2 mm. However, if the enclosure wall 630 is thick enough, the lower edge 622 need not extend beyond the outer bottom surface 632 of the enclosure wall 630.

If the surface 634 is changed to surface 634A by forming a deeper counterbore in the enclosure wall 630, the lower edge 622 may be flush with (or even embedded in) the outer bottom surface 632 of the enclosure wall 630, as the counterbore depth may provide the required distance to prevent ink droplets from wicking back to the outer bottom surface. In addition, the counterbore forms a pocket that provides a second edge to collect ink that may diffuse away from the drip hole 625. Other designs may also prevent ink drops from traveling along the outer bottom surface of the enclosure and spreading or dripping in random places.

As noted above, the projections need not be cylindrical, and may take on different shapes and angles. The protrusions may be oval, square, rectangular, hexagonal, etc., or may be irregularly shaped. Typically, the protrusion shape of the aperture in the bottom of the enclosure should be designed so that the ink remains in the form of droplets and does not travel along the bottom of the enclosure. Thus, the exterior of the outlet aperture may have a narrow edge which projects below at least one bottom surface of the enclosure. The use of a narrow edge minimizes the surface tension between the ink drop and the edge of the aperture so that the ink drop does not stick to the exit aperture. The protrusion of the narrow edge prevents the discharged ink drops/streams from travelling along the bottom of the enclosure.

Fig. 6C shows another example of the drip edge projection 640. As shown, in addition to extending the protrusion 640 a distance away from the printhead enclosure 650, a very narrow edge is used to facilitate the formation of droplets that will quickly fall off the protrusion 640 without wicking back onto the bottom surface 652 of the enclosure wall 650. As an additional precaution, additional drip edges 654 may be included as a backup to the nubs 640, forming pockets 656 to capture any ink that may not drip cleanly from the nubs 640. Other methods of protrusion and drip edge design are possible, including non-circular or symmetrical designs. Fig. 6D shows another example of a drip edge projection 660 that includes a bevel within the hole 665. The protrusion 660 is cut at an angle such that the drip edge is at two different heights. In addition, a pocket 670 may be added to the enclosure wall 680 as needed to prevent ink from wicking back onto the bottom surface 682 of the enclosure wall 680.

As described above, a printhead according to the present disclosure may have more than one printing direction. Accordingly, a structure for removing purged ink from the printhead interior may be used with respect to more than one bottom interior surface of the printhead enclosure. This applies to both implementations that remove liquid ink and to implementations that remove phase change ink from a printhead. Thus, all of the vertical spray orientation embodiments described above may be implemented as horizontal spray orientation embodiments, which may be separate from or together with the vertical spray orientation embodiments.

In a combined embodiment, the aperture is a first aperture in a first interior surface of the printhead enclosure, and the printhead enclosure includes a second aperture in a second interior surface of the printhead enclosure, as well as other corresponding components of the given embodiment, such as a protruding and drop edge, a channel, and/or a heating component. Fig. 7A shows a perspective view (with transparency) of another example of a printhead 730 that may be used for the printhead (printhead 110) in the printing system 100 of fig. 1A, or in other suitable printing systems. Fig. 7B shows an exploded view of the printhead of fig. 7A.

As shown, the printhead 730 includes a front portion 700 of a printhead enclosure that includes a bore 780A, which bore 780A may include a drip edge protrusion and a counterbore. In addition, printhead 730 includes a print engine 710 having an ejection array 712, a circuit board 714, and an ink reservoir 716, as described above for the corresponding components. The jetting array 712 is shown with an opening 720 in the printhead enclosure, but as previously described, the opening 720 may be designed to accommodate a single component with a slot thereon, or the opening 720 may be a slot integrally formed with the printhead enclosure 700. Accordingly, the printhead 730 may also be implemented using the pressurized printhead enclosure systems and techniques described.

Furthermore, since the printhead 730 will operate in a side firing configuration (horizontal firing direction), the draft angle of the printhead enclosure parallel to the length of the firing array 712, along with the improved heating wall 750, can be used to direct ink to the exit orifice at the rear end of the enclosure. Note that the heating wall 750 provides a heating component 754, in this example, the heating component 754 is an extension of the heating wall 545 for the ink reservoir 716. The heating member 754 is sized and positioned so that the distance between the edge 752 and the interior surface of the printhead enclosure 700 is sufficiently small that when the phase change ink melts, the phase change ink remains in contact with the heating wall 750 edge 752 and the interior surface of the printhead enclosure 700 along a channel (structurally formed in the enclosure 700 or by an ink dam) until the phase change ink passes through the aperture 780B. In addition, heating element 754 can include a portion 756 (e.g., as portion 542 in FIG. 5B or portion 456 in FIG. 4A) that extends into bore 780B to keep the phase change ink molten as it passes through bore 780B.

As previously described, the bore 780B may employ the protrusion and drip edge configuration described above. Moreover, these structures may also be used with liquid inks that do not require the heating element 754. Further, in the case of liquid ink, one or more channel structures may be added to the inside bottom (relative to the lateral direction) surface of the printhead enclosure 700 to direct ink to the bore 780B, as described above in connection with fig. 4C and 4D. Moreover, the above-described printhead embodiments may be implemented in conjunction with a pressurized printhead enclosure, as described in detail below.

While this specification contains many implementation details, these should not be construed as limitations on the scope of the invention or of what may be claimed, but rather as descriptions of features specific to particular embodiments of the invention. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Furthermore, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features may in some cases be excised from the claimed combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. Thus, any feature of the above-described embodiments may be combined with any other feature of the above-described embodiments, unless explicitly stated otherwise, or unless explicitly stated otherwise by the knowledge of one of ordinary skill in the art.

Thus, particular embodiments of the invention have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the described systems and methods are applicable to various printer technologies, such as continuous inkjet printers, and in addition to printer technologies, to fluid ejection devices, for example.

Claims

1. A printing apparatus comprising:

a printhead configured to selectively eject liquid through a plurality of nozzles to form an image on a moving substrate; and

a printhead enclosure configured to contain a pressurized air space at least in front of the plurality of nozzles of the printhead;

wherein the printhead enclosure includes a slot aligned with the plurality of nozzles to allow the selectively ejected liquid to pass through the slot when the selectively ejected liquid is ejected toward the moving substrate; and

wherein the printhead enclosure is configured to contain the pressurized air space and to cause an airflow through the slot at a flow rate to prevent dust and debris from entering the slot as the selectively ejected liquid passes through the slot and as the airflow, without the direction of the selectively ejected liquid being impeded by the airflow.

2. The printing apparatus of claim 1, wherein the printhead enclosure includes a smooth and straight inner surface on each of at least two sides of the slot.

3. A printing device according to claim 1, wherein the pressurized air space is set at a pressure level that enables the flow rate of air through the slot to:

interrupting a couette flow caused by the moving substrate passing the print head; and

reducing entrainment of satellite droplets in the Couette flow.

4. The printing apparatus of claim 3, wherein the printhead enclosure includes a curved outer surface on at least a leading edge of the slot.

5. The printing apparatus of claim 4, wherein the slot and the curved outer surface are each integral with the printhead enclosure.

6. The printing apparatus of claim 4, wherein the printhead enclosure includes a separator, and the slot and the curved outer surface are each integral with the separator.

7. The printing device of claim 6, wherein the separator is configured to slide in and out of the printhead enclosure.

8. The printing apparatus of claim 4, wherein the printhead enclosure comprises:

the curved outer surface on each of a leading edge and a trailing edge of the slot, the curved outer surface having a radius of curvature determined to produce a uniform flow distribution between an opening of the slot and the moving substrate; and

a distance between two inner sides of the slot, the distance being determined to prevent the liquid from contacting the two inner sides of the slot and to maintain a consistent, non-turbulent air flow through the slot.

9. The printing apparatus of claim 8, wherein the radius of curvature is between 1.0 and 2.0 millimeters, each of the two inner sides of the slot is greater than 1 millimeter laterally from an edge of any of the plurality of nozzles to overcome boundary layer effects of air along the two inner sides of the slot, and a height between a highest point of the curved outer surface and the plurality of nozzles of a printhead is between 2.5 and 7.0 millimeters.

10. The printing apparatus of claim 1, comprising a pressure source input for pressurizing the printhead enclosure, the pressure source input configured and arranged to direct air from a pressure source to a component in the printhead enclosure that diffuses the air such that a uniform pressure distribution is provided throughout the printhead enclosure.

11. The printing apparatus of claim 10, wherein the printhead enclosure is pressurized whenever the printing apparatus is powered such that the airflow through the slot occurs both during printing and between prints.

12. The printing apparatus of claim 10, wherein the component comprises one or more of a baffle, a perforated plate, a protrusion, a nodule, or a differently shaped object designed to diffuse the air entering the printhead enclosure.

13. The printing apparatus of claim 10, wherein the printhead comprises:

a print engine configured to selectively eject the liquid through the plurality of nozzles;

a printer interface board coupled with the print engine; and

a nozzle plate coupled with the print engine and defining at least a portion of the plurality of nozzles;

wherein the components include components of the printer interface board coupled with the print engine.

14. The printing apparatus of claim 10, wherein the pressure source comprises an air compressor that provides shop air.

15. The printing device of claim 10, comprising the pressure source.

16. The printing device of claim 15, wherein the pressure source comprises a blower.

17. The printing device of claim 15, wherein the pressure source comprises a pressure source assembly comprising:

a filter; and

an air intake device configured and arranged to prevent dust particles from entering the filter.

18. The printing device of claim 1, comprising a pressure source configured and arranged to direct air to one or more surfaces of the diffused air of the printhead enclosure such that a uniform pressure distribution is provided throughout the printhead enclosure.

19. The printing device of claim 18, further comprising a blower assembly, the blower assembly comprising:

a filter located outside of the printhead enclosure; and

the pressure source, wherein the pressure source is located inside the printhead enclosure and is configured to pass air into the printhead enclosure through the filter.

20. A printing system, comprising:

a controller device comprising a user interface;

a print bar configured to receive two or more printheads; and

two or more printheads configured to be attached to the print bar and configured to be communicatively coupled with the controller device, each of the two or more printheads configured to selectively eject liquid through a plurality of nozzles and including a printhead enclosure configured to contain a pressurized air space in front of at least the plurality of nozzles, wherein:

the printhead enclosure includes a slot aligned with the plurality of nozzles to allow the selectively ejected liquid to pass through the slot as the selectively ejected liquid is ejected toward the moving substrate; and

the printhead enclosure is configured to contain the pressurized air space and to cause an airflow through the slot at a flow rate to prevent dust and debris from entering the slot as the selectively ejected liquid passes through the slot and as the airflow, without the direction of the selectively ejected liquid being impeded by the airflow.